This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Breast cancer is the most common cancer in women, accounting for a third of all female cancers. Death from breast cancer is usually due to spread to other organs, which can occur through the blood. We have designed a blood test to detect small numbers of breast cancer cells that have escaped the breast, using a test called K19 RT-PCR. Initial testing in women with breast cancer suggests that high K19 mRNA levels from cancer cells in the blood relate to more advanced cancer. We have also seen that these K19 levels go down to normal levels after treatment with chemotherapy. We believe that the presence of cancer cells in the blood indicated by higher K19 mRNA will be associated with cancer recurrence, and that higher K19 will be found with bigger tumors. To test this hypothesis, we will collect blood samples from patients recently diagnosed with breast cancer, as well as from those with benign breast disease. After measuring K19 mRNA, we will compare average K19 levels across the groups. For those with breast cancer, we will also compare K19 levels to tumor characteristics known to be associated with medical progress. K19 levels will then be followed over time to evaluate trends during cancer treatment, to see if they relate to tumor response, relapse and survival. Subject sample will also be used to develop other early markers of breast cancer, such as a novel nucleic acid assay called BI-PAP-A (S. Sommer) and proteomic profiling (T. Lee).